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-   -   what kind of headwind should a sailboat be able to motor through? (http://www.sailnet.com/forums/general-discussion-sailing-related/102836-what-kind-headwind-should-sailboat-able-motor-through.html)

CanadianNorth 08-22-2013 07:40 PM

what kind of headwind should a sailboat be able to motor through?
 
Thats a broad question,

I have a 1979 Spirit, 28 foot boat with a 15 hp yanmar.

My motor idles and runs fine, up to 5 knots, with minimum headwind (2300 rpm)

However, with strong headwind 30+ knots, the boat simply cannot make headway, the engine struggles, rpms drop and smokes black smoke at times. (drops to 1200-1500) rpm at wide open throttle.

Any thoughts? it is normal for a boat of this size with this engine to be unable to tackle a headwind?

thanks

aeventyr60 08-22-2013 07:47 PM

Re: what kind of headwind should a sailboat be able to motor through?
 
Looks like you found your boats limit.

CanadianNorth 08-22-2013 07:54 PM

Re: what kind of headwind should a sailboat be able to motor through?
 
So that would be normal ? This is my first sailboat, and I only question because I have had idle/black smoke with the engine when I first bought it.

FSMike 08-22-2013 07:57 PM

Re: what kind of headwind should a sailboat be able to motor through?
 
If your engine won't turn more than 2300 rpm at full throttle you may be over propped, or at least have a dirty bottom. You should be able to get at least 2600 out of that engine.
My Yanmar two cylinder will rev about 2700 when conditions are right, i.e. clean bottom, smooth water, etc. That being said I don't think she would push me anywhere into 30 knot winds without falling off and getting some sail assistance, especially with a fierce chop.
The only time I've seen smoke out of my engine was when trying to get some more speed out of the boat when she had a fouled bottom (and propellor). Just had to throttle back and live with it until I cleaned her.

CanadianNorth 08-22-2013 08:00 PM

Re: what kind of headwind should a sailboat be able to motor through?
 
Thanks. The boat was clean when she went in the water 7 weeks ago, but it could be fouling. What length is your boat ?

aeventyr60 08-22-2013 08:03 PM

Re: what kind of headwind should a sailboat be able to motor through?
 
Some of that black smoke may be the built up carbon getting burned up and blown out at higher rpms and hotter running temperature as well as unused fuel. Not sure about the drop in RPM after.

You don't mention the sea state or if your running against the tide, all will impede your progress.

Hows the service history for your engine? Fresh fuel filters, oil filter, oil change, valves adjusted, Exhaust hose checked for blockage? Diesel fuel clean? Tank condition? All stuff that may affect your engine running condition, especially under load. How about your hull bottom and prop condition?

CanadianNorth 08-22-2013 08:18 PM

Re: what kind of headwind should a sailboat be able to motor through?
 
The sea state was choppy, but only a mile from land with offshore winds, so not bad. No tide to speak of.
Hull and prop were clean when she went in the water 7 weeks ago.
Service history is unknown. Last two previous owners cared for the boat well - for what that's worth.
I have owned the boat two months. Previous she was on the hard 2-3 years. Its a 1979 15 HP yanmar. I changed oil, oil filter, fuel filters, new exhaust elbow (long story). Some fuel was in The tank. I had thought I drained it all, but have since run 10 gallons through.
Tank is old, no doubt. And may be an issue.

aeventyr60 08-22-2013 08:30 PM

Re: what kind of headwind should a sailboat be able to motor through?
 
Maybe FSmike's suggestion about the prop is the final answer? I'd enjoy your boat as is and maybe next winter work on the prop sizing issue...You might want to find out what size props others have on their boats.

Ziaduck 08-22-2013 08:30 PM

Re: what kind of headwind should a sailboat be able to motor through?
 
I would check valve lash and consider cleaning the injectors.

smurphny 08-22-2013 09:26 PM

Re: what kind of headwind should a sailboat be able to motor through?
 
Quote:

Originally Posted by FSMike (Post 1078027)
If your engine won't turn more than 2300 rpm at full throttle you may be over propped, or at least have a dirty bottom. You should be able to get at least 2600 out of that engine.
My Yanmar two cylinder will rev about 2700 when conditions are right, i.e. clean bottom, smooth water, etc. That being said I don't think she would push me anywhere into 30 knot winds without falling off and getting some sail assistance, especially with a fierce chop.
The only time I've seen smoke out of my engine was when trying to get some more speed out of the boat when she had a fouled bottom (and propellor). Just had to throttle back and live with it until I cleaned her.

That sounds right, about 500 rpm low and therefore not able to get up to the top of the torque curve/ burning fuel inefficiently.

Lots of things determine a boat's ability to head into the wind under power, including windage of stuff on deck, canvas, hull shape, etc. If you're heading into a 30 knot wind, the waves are usually holding you back more than the wind and that is a hull shape issue.


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